If you've ever tried online dating, or so I'm told, you're likely to encounter a persistent problem: When looking for love, people seem to shade the truth. Nearly 40 is the new 30, and 60 rounds down to farther than even a lovelorn mathematician could countenance. Self-portrayals can get a little grandiose. Words such as mature and fit can mean - well, it's anybody's guess.

Do online-dating sites ever play the same game?

Yes, according to the arbiters at the National Advertising Division of the Council of Better Business Bureaus, who last week dinged eHarmony for stretching some of its own supposedly scientific claims to the breaking point. NAD sided with Match.com's challenge to some of eHarmony's most familiar claims, including:

"Has made more marriages than anyone else."

"Ranks 1st in most satisfied marriages."

"Ranks 1st in most enduring marriages."

NAD's conclusion? While the findings eHarmony cited seem "methodologically sound," they didn't support the company's claims about its relative success. NAD said eHarmony has already dropped another claim Match challenged: calling one of its main studies "independent," even though lead author John Cacioppo is a scientific adviser to the company.

This is the fourth round between the companies since 2006. Twice, Match has challenged eHarmony, and won at least a split decision. Twice, eHarmony has returned the favor, though once it aimed at a Match affiliate, Chemistry.com. Match's parent company also owns OKCupid and other dating sites.

One way or another, almost all dating sites claim to use sophisticated algorithms to match their clients, a promise that has helped the industry come to measure revenue in the billions of dollars.

But this isn't a dispute over eHarmony's claims about its scientific approach to finding you a soulmate. Match only challenged eHarmony's claims about its relative success. So let's go to the details.

Most marriages? Citing Cacioppo's study and other data, eHarmony argued that it has "the most marriages per user or per visitor as compared to its competitors," NAD said.

But, NAD said, potential customers would not necessarily view eHarmony's claim as referring to a higher rate of marriages, rather than a raw number on a site with a very different business model. Instead, it said a likely reading would be that "a higher total number of married couples met on eHarmony's website than met on any other dating website."

NAD said the Cacioppo study showed that 25.04 percent of respondents met a spouse on eHarmony, compared with 24.34 percent on Match - more, but not statistically significant. And NAD agreed with Match's argument that, if matches made on other sites it ran during the period were counted, "the actual difference within the sample is even smaller than reported, or possibly favors Match."

The ad evaluators dispatched eHarmony's other challenged claims with similar Talmudic elan.

It said, for example, that eHarmony's "most enduring marriages" claim suggested it spurs more marriages "that are a life-long bond and are less likely to result in a marital break-up, at any point, than those that began on competing sites" - a claim NAD called too far-reaching for seven years of data.

And "most satisfying marriages"? NAD said that while eHarmony's data showed satisfaction that was better than average and better than Match's, its own study didn't show it as significantly better than Plenty of Fish or an amalgam of smaller sites, including Chemistry, Christian Mingle, and JDate.

Linda Bean, a spokeswoman for NAD, said the industry's self-regulation was designed to tackle claims that can't simply be dismissed as puffery - such as "world's best sandwich."

"When you make a claim that can be proved or disproved, you should have the evidence to do that," Bean told me.

So eHarmony can be expected to tweak the claims that Match challenged. But will it - or any big advertiser - ever give up on shading the truth just a wee bit in its own favor?

Ask someone who's ever tried online dating.

215-854-2776 @jeffgelles